The present invention relates generally to a fillet used with a turbine rotor blade, and more specifically, to a conical fillet used between a rotor blade and a tip shroud.
At least some known turbine rotor blades include an airfoil, a platform, a shank, a dovetail extending along a radial inner end portion of the shank, and a tip shroud formed at a tip of the airfoil. On at least some known airfoils, integral tip shrouds are included on a radially outer end of the airfoil to define a portion of a passage through which hot combustion gasses must flow. Known tip shrouds and airfoils typically include a fillet having a predetermined size and shape at the intersection of the tip shroud and airfoil.
During operation, tip shrouds are stressed because of centrifugal and mechanical forces induced to them during rotor rotation. The fillets are shaped to reduce the stress concentration between the airfoil and tip shroud, but known fillets may also reduce engine efficiency due to drag forces and obstruction produced by the fillets. While the stresses may be reduced by use of constant radius fillets, such a fillet design may be inefficient and adversely impact engine performance. Consequently, there has developed a need for a fillet having customized shape that has a more aerodynamic profile and that increases engine efficiency.